Deficits in social processing, the neurobiological and psychological processes underlying social behavior, are increasingly recognized as key functional components of a range of serious psychiatric conditions. Although chronic drug users have documented social problems, little is known about their social processing capacities. The presence of social processing deficits in drug abusers would likely have substantial implications, including daily function difficulties, problems accessing relationships as rewarding alternatives to drugs, and, importantly, reduced retention and success in psychological treatments for drug use. Identification of social processing deficits can lead to targeted pharmacological or psychological interventions to address them. This project will study social processing in aging, long-term cocaine smokers, a growing group of substance abusers about whom little is known: We have chosen this group to maximize potential study impact and because chronic cocaine use is associated with subtle alterations to brain regions subserving social function. This population remains largely uninvestigated~ with the exception of a pilot study by our group, this would be the first systematic research on psychological functioning in older cocaine smokers. We will employ an innovative, multimodal method to assess social processing in older cocaine smokers, to whom we have ready access via our cocaine laboratory, where older cocaine users regularly volunteer. Regular (e twice/week), long- term (e 20 years use) cocaine smokers between 50 and 60 years old (N=20) will undergo controlled laboratory social processing tests as well as providing self and community observer reports of day-to-day social function following a 4-day inpatient stay. Laboratory measures will include a standardized test of emotion identification, requiring identification of others' emotions from facial expressions. We will also use standardized probes of social reward and social threat in an fMRI protocol to assess brain indicators of processing socially appetitive and aversive material. Three comparison groups will be recruited. Two will be matched for age and demographic factors with the older cocaine group: one of these will also be matched to older cocaine users for alcohol, marijuana and tobacco use (N=20)~ the other will be healthy controls (N=20). With this approach, we will separate effects associated specifically with cocaine use from those related to other risk factors. The third comparison group will be younger cocaine smokers (18-35 years old~ N=20) matched to older cocaine smokers for demographics and current cocaine use. We hypothesize that older cocaine smokers will have: 1) lower day- to-day social function~ 2) lower emotion identification~ 3) decreased neural responses to social reward~ and 4) increased neural response to social threat signals compared to controls. Results will contribute to the empirical basis for developing effective, targeted treatments for the growing population of older cocaine smokers. More broadly, results of this project, which employs techniques validated in related fields but not in drug users, will demonstrate the utility of these concepts in addiction and guide the development of a larger research program.